Predominance of M2 macrophages in gliomas leads to the suppression of local and systemic immunity
Glioblastoma is a highly prevalent and aggressive form of primary brain tumor. It represents approximately 56% of all the newly diagnosed gliomas. Macrophages are one of the major constituents of tumor-infiltrating immune cells in the human gliomas. The role of immunosuppressive macrophages is very well documented in correlation with the poor prognosis of patients suffering from breast, prostate, bladder and cervical cancers. The current study highlights the correlation between the tumor-associated macrophage phenotypes and glioma progression. We observed an increase in the pool of M2 macrophages in high-grade gliomas, as confirmed by their CD68 and CD163 double-positive phenotype. In contrast, less M1 macrophages were noticed in high-grade gliomas, as evidenced by the down-regulation in the expression of CCL3 marker. In addition, we observed that higher gene expression ratio of CD163/CCL3 is associated with glioma progression. The Kaplan–Meier survival plots indicate that glioma patients with lower expression of M2c marker (CD163), and higher expression of M1 marker (CCL3) had better survival. Furthermore, we examined the systemic immune response in the peripheral blood and noted a predominance of M2 macrophages, myeloid-derived suppressor cells and PD-1+ CD4 T cells in glioma patients. Thus, the study indicates a high gene expression ratio of CD163/CCL3 in high-grade gliomas as compared to low-grade gliomas and significantly elevated frequency of M2 macrophages and PD-1+ CD4 T cells in the blood of tumor patients. These parameters could be used as an indicator of the early diagnosis and prognosis of the disease.
KeywordsGlioma Tumor-associated macrophages CD163 CCL3 PD-1
Fluorescence-activated cell sorting
Glyceraldehyde 3-phosphate dehydrogenase
Human Leukocyte Antigen—DR isotype
Peripheral blood mononuclear cells
Programmed cell death protein 1
The Cancer Genome Atlas
Transforming growth factor-beta
We thank Dr. Debajyoti Chatterjee, Gurpreet, Ishwar and Alka from Department of Histopathology, Postgraduate Institute of Medical Education and Research, Chandigarh, India for the helpful suggestions for doing immunohistochemistry.
JNA and AV conceived the project. AV, TA and NK performed experiments. AV, TA, NK, JNA, BDR, MKT and DC analyzed data. AV, JNA, NK, MKT and SS wrote the manuscript. All authors assisted in editing the manuscript and approved its final version.
Authors are grateful to the Council of Scientific and Industrial Research (CSIR), Department of Biotechnology (DBT), Indian Council of Medical Research (ICMR), India for financial support. Aurobind Vidyarthi and Tapan Agnihotri received fellowships from the CSIR, Nargis Khan from DBT, and Sanpreet Singh from ICMR.
Compliance with ethical standards
All authors have declared no conflicts of interest.
All procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional committee. The study was approved by the Postgraduate Institute of Medical Education and Research, Chandigarh, India ‘Institutional Ethical Committee’ (Ref. No. PGI/IEC/2012/1498-99) and ‘Institutional Biosafety Committee of the Institute of Microbial Technology’ (Ref. No. 1/IEC/1/9-2014), Chandigarh, India.
Written informed consent was obtained from all individual participants and close relative of the deceased (For cadavers) included in the study for using the specimens for research and publication.
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